/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public int maxDepth(TreeNode root) {
        if(root==null) return 0;
        return Math.max(maxDepth(root.left),maxDepth(root.right))+1;
    }
}

class Solution {
    private boolean tag = true;
    public boolean isBalanced(TreeNode root) {
        maxDepth(root);
        return tag;
    }
    public int maxDepth(TreeNode root){
        if(root==null)return 0;
        int left=maxDepth(root.left);
        int right=maxDepth(root.right);
        if(Math.abs(left-right)>1){
            tag=false;
        }
        return 1+Math.max(left,right);
    }
}